first=float(input("请输入第一个数:"))
second=float(input("请输入第二个数:"))
operator=input("请选择运算符：+—*/:")
if operator =='+':
    print(first+second)
elif operator =='-':
    print(first-second)
elif operator =='*':
    print(first*second)
elif operator =='/':
    if second == 0:
        print("除数不能为0")
    else:
        print(first/second)